The present invention relates to a monopolar end-plate for a fuel cell of the type having a proton-exchange membrane.
A fuel cell having a proton-exchange membrane is a device for producing electricity by means of an electrochemical reaction between a fuel, for example, a gas containing hydrogen, and an oxidant, for example, a gas containing oxygen, separated by a wall which is constituted by a solid electrolyte.
In a device of this type, when the fuel is a hydrogenous gas and the oxidant is an oxygenous gas, the hydrogenous gas and the oxygenous gas react in order to form water whilst generating an electrical current which may be used for various applications.
Generally, a fuel cell is constituted by a stack of reactive cells or elementary cells which are each constituted by an electrode/membrane assembly which is inserted between two bipolar plates which comprise channels which are intended for the circulation of, on the one hand, a fuel and, on the other hand, an oxidant, and finally a heat-exchange fluid such as water. The electrode/membrane assembly is a multi-layer material which is known per se and which comprises a layer which is constituted by a membrane of solid electrolyte which is itself arranged between two active layers which constitute, on the one hand, a cathode and, on the other hand, an anode, which are themselves coated with two outer layers and a diffusion layer.
The stack of elementary cells is generally retained in a state secured between two terminal plates which are flange-mounted by means of pins which extend from one terminal plate to the other and which extend through the stack of elementary cells.
At one of the ends of the fuel cell, an anode monopolar plate is located which is fitted to a current collector and, at the other end, a cathode monopolar plate which is fitted to another current collector. The assembly is held mechanically by the terminal plates and tensile rods of the assembly.
Generally, monopolar end-plates are produced from materials which provide good properties of resistance to corrosion and which have good electrical conductivity, such as, for example, carbon-containing materials such as graphite, graphite impregnated with polymer or flexible sheets of graphite.
These components are generally shaped by means of machining or moulding in order to define, on the one hand, on an active face, circulation channels for reactive gases and, on the opposing face, a surface for contact with the current-collecting plates.
This technique has the disadvantage in particular of requiring the production of specific monopolar end-plates which are distinguished from the bipolar plates produced for the stack assembly of the cell. The costs are consequently significantly increased.